The present invention relates to an electro-hydraulic power-assisted steering system for vehicles, in particular for electric vehicles. It also relates to an electric vehicle, in particular an electric public transport land vehicle, of the bus or tyred tram type, fitted with such a system.
The field of the invention is the field of electric public transport land vehicles of the bus or tyred tram type, fitted with rechargeable electrical energy storage modules in order to supply at least one electric motor of said electric vehicle.
Today, most electric vehicles are equipped with a system for assisting the steering of the vehicle, commonly called “power-assisted steering”. This becomes indispensable in the context of heavy vehicles, such as public transport vehicles of the bus type.
In current vehicles, and in particular in electric public transport vehicles, the vehicle's power-assisted steering is provided by an electro-hydraulic system comprising a hydraulic fluid reservoir, a hydraulic actuator for operating a steering rack shaft of the vehicle, and an electric pump-motor pumping the hydraulic fluid to the actuator according to the driver's requirements. The electric pump-motor is supplied by a high-voltage signal of the order of 230 Volts.
Now, using a high-voltage pump-motor operating at 230V is hazardous, due to the voltage used.
In addition, in electric vehicles, this requires voltage conversion in order to obtain the 230V supply voltage from the high-voltage signal delivered by the batteries of the vehicle (generally 400V), which requires the use of a specific voltage converter which is a costly element with a large space requirement.
Moreover, when the electric pump-motor fails, the power-assisted steering is completely lost, which on the one hand is not very ergonomic and on the other hand can be hazardous for the people on board the vehicle.
A purpose of the invention is to overcome these drawbacks.
Another purpose of the invention is to propose a safer power-assisted steering system for an electric vehicle.
Another purpose of the invention is to propose a power-assisted steering system for an electric vehicle which is more cost-effective and simpler to incorporate into an electric vehicle.
A further purpose of the invention is to propose a power-assisted steering system for an electric vehicle offering improved failure management.
Yet another purpose of the invention is to propose a power-assisted steering system for a heavy vehicle, of the passenger bus type, which does not require a dedicated power converter, i.e. in addition to a converter with which the vehicle is already equipped.